The SEC is looking into the fee practices of private equity firms Carlyle Group and Apollo Global Management.

The investigations, which remain informal, were unearthed in a Feb. 10 Carlyle filing that states the SEC requested “additional information” about the firm’s “historical monitoring fee practices.”

Meanwhile Apollo’s November 10-Q filing revealed the SEC had also asked for more information regarding its “disclosure to limited partners of the acceleration of certain special fees,” Chief Investment Officer reports. Carlyle raised $550M for a new real estate fund last month.

Meanwhile, both firms say they’re fully cooperating with the SEC’s requests. Fellow private equity giants Blackstone and KKR were hit with a combined $69M in settlements by the SEC last year for similar charges over improper fee disclosures.

In October, SEC Chair Mary Jo White said the regulator will continue to look closely at private equity fee and expense practices, saying investors deserve to have the “information necessary…to make an informed investment decision." [CIO]